Exposing asymptomatic potential issues leads to medical care that often does not meet out standards for medical tradeoffs. Chemo is nasty, even the most minor surgery has risks. We endure the risks because we are addressing either major health issues or other dire uncertainties. Using our heavy duty treatments for issues without any symptoms at all would, normally, cause the patient suffering in excess of what would be justified. Chemo is a life saver when it's saving lives -- if the alternative is no symptoms, it just ruins your life for a profoundly uncertain upside.